Ship-Mode Current Limiting Circuit for Battery Shoot-Through
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Solution Overview
Problem
Battery charging circuits experience shoot-through current when entering ship mode, which can damage batteries and pose safety risks due to over-charging, despite components being turned off, as capacitance in loads creates voltage differences that allow current to flow through body diodes.
Innovation Solution
A circuit with a logic circuit, comparators, and an AND logic circuit that determines voltage conditions to enable ship mode by comparing input voltage, battery voltage, and supplemental voltage thresholds, outputting control signals to prevent shoot-through current by ensuring transistors remain in non-conductive states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If components are turned off to achieve low standby current, then standby current is reduced, but shoot-through current can flow through body diodes due to voltage differences caused by load capacitance
Solution Approach 1:
The patent applies preliminary action by checking voltage conditions before enabling ship mode. The control circuit compares input voltage and battery voltage against threshold values in advance, ensuring that ship mode is only enabled when voltages are within safe ranges, thereby preventing shoot-through current from occurring in the first place
Solution Approach 2:
The patent implements feedback by continuously monitoring input voltage and battery voltage through comparators, and using this feedback information to control the enablement of ship mode. The control circuit adjusts the ship mode state based on real-time voltage conditions, preventing shoot-through current by responding to voltage changes
2Use of energy by moving object
If ship mode is enabled to reduce power consumption, then standby current is reduced, but battery safety is compromised due to potential shoot-through current and over-charging
Solution Approach 1:
The patent performs preliminary voltage checks against predefined thresholds before allowing ship mode to be enabled. This ensures that input voltage is sufficiently high and battery voltage is within safe charging limits, preventing both shoot-through current and over-charging conditions that would compromise battery safety
Solution Approach 2:
The patent introduces voltage threshold comparisons as intermediary checks between the ship mode enable request and the actual enabling. The comparators and control circuit act as intermediaries that verify voltage conditions, adding a safety layer that prevents direct enabling of ship mode under unsafe conditions
Data Source
AI summary
Aspects of the disclosure provide for a circuit. In at least some examples, the circuit includes a logic circuit, a first comparator, a second comparator, and an AND logic circuit. The logic circuit has an output and the first comparator has a first input coupled to an input voltage (VIN) pin, a second input configured to receive a Vin under voltage lockout (VINUVLO) threshold value, and an output. The second comparator has a first input coupled to a power middle (PMID) pin, a second input coupled to a battery pin, and an output and the AND logic circuit has a first input coupled to the output of the logic circuit, a second input coupled to the output of the first comparator, a third input coupled to the output of the second comparator, and an output coupled to an input of a field-effect transistor (FET) control circuit.